A hybrid vehicle having an engine and an electric motor mounted as the source of vehicle driving power may be configured to allow selection of a running mode with the engine stopped, and a running mode with the engine operated. When such a hybrid vehicle attains a running state where the engine is required during running with the engine in an inactive state, the engine will be started automatically. When the hybrid vehicle then attains a running state where the engine is no longer required, the operating engine is automatically stopped. Thus, the engine is operated automatically in an intermittent manner.
Japanese Patent Laying-Open No. 2009-18743 (PTD 1) discloses control of a hybrid vehicle capable of generating the electric power for charging a battery from the engine output, directed to reducing the frequency of starting and stopping an engine for battery charging when the vehicle is at a halt for a long period of time.
Japanese Patent Laying-Open No. 2007-218107 (PTD 2) discloses control of determining whether to permit execution of idling stop based on the SOC (State of Charge) and SOH (State of Health) of the battery to store electric power used in engine startup. Particularly, the threshold values of the SOC and SOH used for the determination of allowing/disallowing idling stop are modified based on the execution count of idling stop within a predetermined period of time after starting battery usage (claim 2 in PTD 2). Accordingly, execution of idling stop is suppressed.
Japanese Patent Laying-Open No. 2004-186087 (PTD 3) discloses a power supply system including a power storage device having the SOC regulated within a predetermined range, wherein the SOC of the power storage device is increased when the number of times the SOC attains the lower limit or approaches the lower limit of the SOC regulation range.